Tech Tops in Transportation Materials Research

As an expert in concrete, though, he wonders whether these new deicing chemicals are eating away the highways.

The South Dakota Department of Transportation (DOT), along with eight other state DOTs, have hired the Michigan Tech faculty member and researcher to address that concern.

“Magnesium chloride and calcium magnesium acetate, among other chemicals, have proven very effective at deicing,” Sutter says. “But there is a lot in the literature about the negative effect of magnesium chloride on portland cement (the most common ingredient in concrete roads).

“The question is about the concentration of magnesium being used. Is it enough to worry about?”

To find out, he will use one of the best collections of optical equipment in the country for analyzing pavement materials.

Michigan Tech has an array of sophisticated optics, including an environmental scanning electron microscope (ESEM), allowing researchers to examine how quickly magnesium penetrates concrete. The ESEM, which magnifies objects thousands of times, can detect cracks in the concrete’s microstructure, which could weaken the roadway.

The ESEM and an x-ray microscope came from a $700,000 National Science Foundation equipment grant. A wide range of fields have applications for the ESEM, including forestry, biology, biomedical engineering, chemistry, chemical engineering and geology—making it a campus-wide interdisciplinary resource.

This collection of sophisticated instruments is part of the Michigan Tech Transportation Institute (MTTI). Ten faculty and 20 staff members participate in the institute. They have expertise in a number of areas, including:

• materials used in transportation systems
• factors affecting the durability of highway systems
• the composition of aggregates used in transportation system materials
• developing software and training workshops for practicing transportation engineers.

“We do more research for the Michigan Department of Transportation (MDOT) than any of the other state universities,” said Tom VanDam, associate professor of civil and environmental engineering and director of the Transportation Materials Research Center. He says Michigan Tech has at least $3 million under contract with MDOT at any given time.

____________

Tess Ahlborn’s (left) research
focuses on making prestressed
concrete beams for bridges
more durable.
____________

“In some areas of expertise, we have the best facilities you will find anywhere,” VanDam said. “One is in the asphalt area—binder and mixture characterization. The second is in material characterization and our microscopy capabilities. People see our equipment and their jaws drop.”

Like Sutter, VanDam works in concrete durability.

“Portland cement is the most common building material on the planet,” he said. “The Romans formed cement through a combination of volcanic ash and calcite limestone. I was a Peace Corps volunteer in Africa and I could go way back in the bush and still find bags of cement. It is everywhere, but its complexities are still being explored.

“We study the interaction between how the cement, as it hydrates, forms the solids that make concrete what it is—a rock-like mass. How are aggregates binding together? What is causing things to fall apart, crack, or suffer other distress? We can study that on a microstructural level.”

One application for this research was funded by the federal highway research program. VanDam and Sutter looked at the use of accelerators—hardeners mixed with concrete to make it dry faster. State DOTs use these additives to patch a concrete highway, while closing it only for a few hours.

“There have been notable failures of these materials in 6-10 years, when patches disintegrate,” VanDam said. “We’re looking at various mixes and their durability.”

Along these same lines, Tess Ahlborn focuses on pre-stressed concrete beams for bridges. Part of her research focuses on the reinforcement rods, or “rebar” embedded in the concrete.

Some rebar is steel, some epoxy coated, some stainless steel.

“Which of these make our highway systems more durable?” asks Ahlborn, an assistant professor of civil engineering. “Epoxy-coated bars may not anchor as well, for example. Stainless steel is expensive, but maybe not so expensive over the lifetime of the structure.”

Ahlborn is also developing guidelines for bridge inspectors. The project, funded by MDOT, will create more standardized inspection criteria state-wide.

“Over time, pre-stressed concrete beams deteriorate. But when does it become a concern? We developed a manual that describes a series of different levels of deterioration, from cosmetic to things that are problems. We used photos to demonstrate each of 12 levels, so inspectors can compare. This will provide better consistency across the state.”

In 2002, Michigan Tech also received $750,000 from Congress to fund the Institute of Aggregate Research, which is part of MTTI. Researchers will focus on evaluating sources of aggregates—the fine sand, crushed rock and slag used to make concrete.

The aggregate institute will look to develop quick, inexpensive methods to determine the quality of aggregates in rock quarries and gravel pits. They will also look at a variety of environmental issues surrounding aggregate production, transportation and reclamation.

“Partnerships are making all of this work,” VanDam said. “Too often, universities seem to encourage Lone Rangers. We are so much stronger as teams.”

For more information, see www.trans.mtu.edu.

Karl Peterson is the staff member that makes the
Environmental Scanning Electron Microscope work.

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